Bangladesh , officially the People's Republic of Bangladesh , is a sovereign country in South Asia. It forms the largest and eastern portion the ethnolinguistic region of Bengal. Located at the apex of the Bay of Bengal, the country is bordered by India and Myanmar and is separated from Nepal and Bhutan by the narrow Siliguri Corridor. With a population of 166.2 million, it is the world's eighth-most populous country, the fifth-most populous in Asia and the third-most populous Muslim-majority country. The official Bengali language is the seventh most spoken language in the world, which Bangladesh shares with the neighbouring Indian states of West Bengal, Tripura and Assam . Three of Asia's largest rivers, the Ganges , the Brahmaputra and the Meghna, flow through Bangladesh and from the fertile Bengal delta—the largest delta in the world. With rich biodiversity, Bangladesh is home to 700 rivers, most of the world's largest mangrove forest; rainforested and tea-growing highlands; a 600 km coastline with the world's longest beach; and various islands, including a coral reef. Bangladesh is one of the most densely populated countries in the world, ranking alongside South Korea and Monaco. The capital Dhaka and the port city of Chittagong are the most prominent urban centres. The predominant ethnic group are Bengalis, with a politically-dominant Bengali Muslim majority, followed by Bengali Hindus, Chakmas, Bengali Christians, Marmas, Tanchangyas, Bishnupriya Manipuris, Bengali Buddhists, Garos, Santhals, Biharis, Oraons, Tripuris, Mundas, Rakhines, Rohingyas, Ismailis and Bahais.